Within the industry, there are used many kinds of belt conveyors of the type that comprises an endless belt as well as a plurality of rollers, at least one of which consists of a drive roller, another of a tension roller, and the other ones of a varying number of deflection rollers. Within many processing industries, e.g., for the preparation and processing of food, belt conveyors are found, the belts of which consist of steel and therefore have good properties in respect of strength, service life and hygiene. However, in such conveyors, at times problems arise so far that the belt may tend to be displaced laterally in relation to certain rollers, which should be passed, and thereby deviate from the ideal path in which the belt reliably is centred in relation to the rollers. This phenomenon may in particular arise when the belt should run around a tension or drive roller at one end of the conveyor. Such displacement tendencies may, among other things, arise as a consequence of uneven load on the belt, but also for other reasons.
In order to manage the above-mentioned problems, adjustment devices of the type initially mentioned are used since long, viz. a roller that is rotatably mounted in a cradle and tiltable by means of a force generator that brings the cradle to be turned in relation to the stand around an axis extending perpendicularly to the rotation axis of the roller. The rollers of such adjustment devices are commonly denominated “tilt rollers” by those skilled in the art. By fitting such a tilt roller upstream the drive or tension roller, which should be passed by the belt, and let the tilt roller co-operate with sensors that detect the centring of the belt, the path of the belt can be corrected by means of readjustment of the tilt roller in a suitable direction and angle in relation to the belt path.
However, a disadvantage of previously known adjustment devices, which are fitted to the frame work carrying the belt conveyor in its entirety, and which are located either above or below the belt, is that the force generators occupy an obstructively large space in and around the frame work. Thus, in previously known belt conveyors, vertically fitted piston-cylinder mechanisms are used, which are pivotally connected with the two opposite ends of the cradle and have the purpose of lowering and raising, respectively, the same depending on the desired setting angle and setting direction of the tilt roller. When the tilt roller of the adjustment device is fitted for actuation of the upper part of the belt, said piston-cylinder mechanisms will protrude upward fairly high from the frame work of the conveyor. If the tilt roller is, on the other hand, fitted for actuation of the lower part of the belt, the mechanisms occupy space inside the frame work, whereby the machine construction in its entirety becomes complicated.